The invention relates to the technical field of civil engineering machines presenting skips, buckets or other receptacles capable of scraping, removing, shifting materials or other items for their removal from a given place to other operating stations using civil engineering machines.
The prior art discloses how to place, on the abovementioned skips, buckets, receptacles and similar items, appropriate adapter noses which are capable of receiving removable teeth having a matching profile. These teeth are in direct contact with the materials, items to be removed, to scrape, and are consequently subject to rapid wear due to their severe use. The adapter noses formed on the skips, buckets and other receptacles are male parts integral with the lip of the preformed skip, bucket or receptacle, and are made added on or one-piece during the conformation of the bucket, skip or receptacle, or other particular tools. The teeth which are added on constitute female parts established in shapes matching the profiles of the adapter nose(s) to engage therein. The need to replace the teeth, to contend for their wear, requires a connection between the wear parts and the corresponding adapter nose. In the prior art, this connection is proposed by numerous manufacturers in the form of a keying which may be either direct metallic, or assisted by an elastic material.
Experience shows that, irrespective of the nesting and connecting systems employed, it is impossible, because of the manufacturing tolerances which impose clearances to permit the assembly of the teeth on their adapter support, added to those which are formed by the ramming and the service wear of the contact zones, to prevent any possible movement of the tooth on its adapter support.
Thus, the teeth are connected to their adapter noses by keying to permit their removal and replacement after the teeth are worn. The horizontal, lateral, oblique or miscellaneous loads inherent in the applications and uses also cause damage to the tooth-nose-adapter connection, but also to the keying. The tooth is observed to pivot with respect to the adapter nose, causing damage thereto by wear due to friction.
These two major problems are observed to combine or not, depending on the arrangements of the teeth and adapters.
On the first problem and in the prior art, the tooth-adapter nesting configuration is often found, as shown in FIG. 1, in the form of a pyramidal or frustoconical nesting.
During the application of the crowding force (FC), shown in FIG. 2, which is the highest stress received during the loading of skips and buckets, there is a tilting movement in the direction indicated by (R). The tooth tends to tilt on its adapter support and the lower wall of the cavity (Ci) bears very strongly on the lower body of the adapter support.
As long as the clearances between tooth and adapter are low, the allowable tilt of the tooth is also low and the force on the contact zone (Ci) is acceptable for the strength of the tooth case.
A moment arrives when the clearance (J) between the tooth and its adapter support is such that it may exert a wedge action in the tooth case, which then cracks, tears or bursts (FIG. 2), making the tooth inoperative.
The strongest configuration is also known, according to FIG. 3. The nose of the adapter support, in its front part, has a stabilisation flat, and the back of the adapter support comprises housings receiving the two lugs of the tooth. The clearance established in the production of the parts is such that J2 between the upper and lower sides of the socket is higher than that produced at the stabilisation flat and the lugs (J1). J2>J1.
During the application of the crowding force (FC) to this configuration also shown in FIG. 4, the tooth bears on the stabilisation flat to which a force (FPS) is applied, initiating a rotation along (R), blocked by the contact of the tooth lugs which transmit the force (FO) to their housings of the adapter support. Accordingly, the bearing force at (Ci) is reduced and the risk of bursting the tooth case is lower than in the previous case (FIGS. 1 and 2).
However, experience shows that in use, the stabilisation flats and the tooth lug housings become worn by the ramming and the friction, and the clearance which then exists with the corresponding faces of the new replacement teeth increases considerably. The advantage of absorbing the loads, by the support of the tooth lugs in their housings in the adapter support, no longer exists, producing the previous case shown in FIGS. 1 and 2.
If we now return to the second problem, the problem of keying, the following may be observed.
According to known practice, teeth keying systems, to guarantee their tension on their adapter supports, are placed either vertically or horizontally. Their keys may or may not be assisted by an elastic element. Placed horizontally, they have the drawback of difficult access due to the too close presence of the neighbouring adapters. Placed vertically, they are liable to lose keys, particularly via the bottom.
The elastic elements of the abovementioned type are sometimes made in the form of tubular sleeves and two systems are known:
The first concerns a vertical key formed by two cylinders screwed to one another, one forming a bolt and the other a nut (FIGS. 5, 6 and 7). A rubber tube is placed between the two. By screwing the two elements forming the key closer together, the rubber tube tends to be crushed and expanded. It is positioned in a recess provided in the adapter body where it can expand, and stiffen under the screwing pressure. This ensures the retention of the key in service. On the other hand, the rubber, whereof the position is imposed by the recess in the adapter, places the metal elements forming the key in a random position with respect to the orifices of the tooth, where they cannot systematically be found in a back contact position to guarantee retention of the tooth. In addition, in practice, in the case of a favourable random position of the key, there is little or no rear bearing force for retaining the tooth.
The second is placed horizontally (FIGS. 8 and 9). A rubber tube is introduced into its housing in the adapter. After installing the tooth, a cylindrical rod forming a key is introduced via one or the other of the orifices of the tooth. The rod diameter is slightly higher than the inside diameter of the rubber tube to generate tightness in order to ensure the retention of the key during service.
This device, which has the drawbacks of the previous one, concerning the random position of the key with respect to the orifices of the tooth and the lack of retaining force, is only employed in special cases where there is no tooth extraction force. It is only employed in so-called RIPPER applications in which the teeth are only loaded in the forward direction. The penetration work direction, on the contrary, tends to press the tooth strongly against its adapter support.
The principle of sandwich keys is also known, as described by the Applicant, placed particularly with a particular structure of two mutually displaceable components and between which an elastically deformable material is placed. Such a key is described in patent PCT WO 2004/035945 to the Applicant. This type of key is however specific to a configuration of the tooth with a skirt surrounding and protecting the adapter.
The Applicant also uses a particular method called “STICKEY method”, the subject matter of patent EP No. 618.334, which provides for the insertion of a key in a vertical plane, the key being tapered from the top downwards, and receiving the assembly material in an appropriate chamber. The latter is in the form of a resin which solidifies to form a retaining sleeve between the tooth and the adapter.
In all the known cases of the Applicant described above, the key is fully embedded in the connecting volume between the tooth and the adapter. Specific tools are therefore needed to remove it and/or extract it, or even to heat the elastic material to make it liquid so as to permit the removal of the key.